Antistray arrangement for radio communication



e. 'warenhuis-w:

UNITED STATES `PATENT OFFICE AN TISTRAY ARRANGEMENT FOR RADIOCOMMUNICATION Fritz Klutke, Berlin-Johannisthal, Germany, as-

signor to Allgemeine Elektricitats Gesellschaft Friedrich Karl, Berlin,Germany, a corporation of Germany Application March 14, 1936, Serial No.68,787 In Germany -March 14, 1935 7 Claims.

This invention relates to a new and novel receiving tube circuitarrangement which contains a rst oscillation circuit which is detuned inreference to the incoming wave, while the plate circuit of the same tubecontains a second oscillation circuit tuned to the same frequency, andin series therewith is a third oscillationv circuit which is tuned tothe incoming wave. This circuit organization could also be combined witha push-pull scheme in which the grid of one tube is impressed with thesum total comprising the stray or interfering Wave and the incomingwave, while the grid of the second tube is impressed only with the straywave.

It is not always an easy matter to employ the customary ways and meanssuccessfully for reducing aperiodic interference in radio frequency Atelegraphy and telephony. It is of some assistance to adopt methods ofincreasing the selectivity, also to render the antenna directional inits characteristic. The ideal of interference elimination is not,however, attained by such methods.

Accordingly, it is an object of my invention to provide a circuitarrangement which will more effectively eliminater stray interference of.an aperiodic nature.

It is another object of my invention to improve the signal-to-noiseratio in a receiving circuit.

In carrying out my invention I preferably pro- 'vide a first tunedcircuit upon which the incoming energy is impressed. 'I'his inputcircuit is connected in a conventional manner between the control gridand the cathodeof an eleclnd'i"dis-k charge tube amplifier stage. Theunconventional method which I employ, however, is to tune theinputcircuit of this amplifier stage to a frequency different from that ofthe incoming signal frequency. I also tune the output circuit ofthiaamplier stage by the use of two oscillatory or tank circuits whichare series connected between the cathode and anode of the tube. One ofthese tank circuits is tuned to the same frequency as the tuned inputcircuit. The other tank circuit is tuned to the incoming signal wave.

Now, if aperiodic interference or stray waves happen to be impressed onsuch a circuit organization, they will excite the tuned grid' circuitofthe rst tube at its natural frequency. In other words, the interferenceis transmitted in the form of an oscillation having the frequency towhich the oscillation circuit on a certain resonant portion of the gridcircuit on the input tube L- (Cl. Z50- 20) plate circuit which has beentuned to the identical. frequency and whichv represents for thisfrequency a very high impedance, the entire drop of voltage for theinterfering wave will occur in this resonant portion.- I have found itadvan tageous, therefore, to place a second resonant circuit in serieswith the rst resonant circuit and to tune this second circuit to thefrequency to be received. The result is that practically no drop ofpotential of the interfering wave will take place. If, then, thefrequency to be received is taken off at the said second tank circuit, areceiving wave'being practically free from stray interference will beobtained. If, on the other hand,l sinuous incoming waves happen toimpinge upon the first tank circuit, forced oscillations will be set uptherein winch are of the same frequency as the incoming currents.v'Ihese forced oscillations, as well known in the art, are amplifiedbythe tube, and they are made available across the terminals of thedoubly tuned plate circuit of the tube which has been tuned to theincoming wave as above stated.

Owing to the fact that one foregoes the chance of tuning the firstoscillation circuit to the incoming wave, the received amplitude, to besure, will be lower than in a case where the said oscillatory circuit istuned to the incoming wave.

However, since the stray amplitudes are .at thetially raised in thearrangement here disclosed.

This invention will best be understood by referring to the accompanyingdrawing, in which:

Fig. 1 is a circuit diagram of this invention,

y showing the three oscillatory circuits;l while Fig. 2 is acircuitdiagram of a push-pull arrangement employing rectiers. Referring now indetail to the drawing: Figure 1 shows a tube circuit organizationaccording to this invention which embodies the characteristic featuresof the invention. The grid circuit of the tube R includes an oscillationcircuit si whichhas been set to the frequency fl having a valuedifferent from the incoming frequency. The platey circuit contains .anoscilla# tion circuit S'I which is also tuned. to the frequency fl, andin series therewith is provided a second oscillation circuit s2 which istuned to the incoming frequency f2. Across the terminals --of the saidsecond oscillation circuit is taken-0E the signal frequency and the sameis thence fed to other parts of the receiver. The oscillation circuit s2is variable as known in the art in order that it may be adjusted to theparticular frequency to be received. In order to make sure so thatfrequency f2 will always be sufliciently far apart from frequency fl,the latter either may be chosen outside the range or wave band to bereceived with a given receiver apparatus, or else the oscillationcircuits may be so coupled with each other that they will always bealtered jointly so that the proper distance apart will be insured. Forexample, the tuning means may be mechanically coupled together asindicated diagrammatically in Figure 1.

According to a further object of this invention, the circuitorganization illustrated in Figure 1, whenever extremely strong straysignals are dealt with, may be expanded in so far as the stray frequencyalone as well as the interfering wave and the useful or signal frequencyare jointly impressed each upon the grid of a tube, with the platecircuits of both tubes being connected pushpull fashion. The tubes inthis scheme are used to operate as rectiers so that in the plate circuitof one tube, as known in the prior art, either the sum or the differenceof signal frequency and stray frequency is produced, while in the platecircuit of the other tube the stray alone arises. The superposition ofboth currents then results in the signal frequency alone. Experience hasshown that such a push-pull scheme can be adjusted to any desired degreeof exactness so that in this manner practically perfect elimination ofinterference is feasible:

Figure 2 illustrates a circuit arrangement comprising the last namedfeature. Associated with the oscillation circuit sl in the plate circuitof the input tube is the grid circuit of tube R2 to which, as will benoted, only the stray wave is fed, While with the series schemecomprising both oscillation circuits the grid circuit of tube R3 isconnected, the latter circuit thus being impressed with the aggregatesignal and interference frequencies. What will then arise in thesecondary circuit of the transformer Ue is only the signal frequency.

The basic idea of this invention, as to the rest, is not confined to theexempfied embodiment hereinbefore described, in fact, it may be applied,for instance, also in cases Where crystal or contact type rectiers areemployed in lieu of the two tubes R2 and R3 which act as rectifiers.

I claim:

1. An arrangement for eliminating interference in the reception ofradionfrequencnsignals. comprising an electron discharge tube having atuned.

tuned input circuit and the two said oscillation circuits in the outputcircuit.

3. A receiving circuit to reduce undesired stray Waves of radiofrequency signals comprising a first oscillation circuit which isdetuned with re- 5 spect to the frequency of a desired incoming wave, anelectron discharge device having anode grid and cathode, the grid andcathode of said device being connected to said first oscillationcircuit, a second and third oscillation circuit connected in 10 serieswith each other, at least one of which is tuned to the desired frequencyto be received, and the other connected to the anode of said electrondischarge device.

4. A receiving circuit to reduce undesired stray 15 waves of radiofrequency signals comprising a rst oscillation circuit which is detunedwith respect to the frequency of a desired incoming wave, an electrondischarge device having anode grid and cathode, the grid and cathode ofsaid device 20 being connected to said first oscillation circuit, asecond and third oscillatigncircuit Aconnected Y in series with eachother, at least QneNof Awhich variable, the other beingconnectedjotheuanode of said electron discharge devic and detuned 2 5with respect to the frequency of a desired incoming wave.

5. An arrangement for eliminating interference in the reception of radiofrequency signals comprising an electron discharge tube having a'tunedinput circuit and an output circuit having therein two differently tunedoscillation circuits, said input circuit and one of said oscillationcircuits bei n g t-uned to substantially the same frequency and theotlrof said oscillation circuits being tuned to a different frequency atwhich it resonates with an incoming signal frequency, and means forsimultaneously varying the tuning of each of said tuned circuits.

6. An arrangement for eliminating interference in the reception of radiofrequency signals comprising an electron discharge tube having a tunedinput circuit and an output circuit having therein two differently tunedoscillation circuits, said input circuit and one of said oscillationcircuits being tuned to substantially the same frequency and the otherof said oscillation circuits being tuned to a different frequency atwhich it resonates with an incoming signal frequency, a rectifierconnected to each of said oscillation circuits and means for combiningthe output from each of said rectiers in phase opposition.

7. A device for eliminating interference in the reception of radiofrequency signals, an electron discharge tube amplifier stage havingtuned input and output circuits, said output circuit including twodifferently tuned tank circuits, one of said circuits being tuned tosubstantially the same frequency as said input circuit, and the other ofsaid tank circuits being tuned to the signal frequency, a rectifierconnected to each of said tuned circuits, means for impressing bothstray frequencies and signal frequencies on one of said rectiers andmeans for impressing signal frequencies only on the other of saidrectiflers, and means for combining the output from each of saidrectiers inphase opposition.

- FRITZ KLUTKE.'

